Breast cancer is a disease situated as a superior cause for female lethality due to cancer, however, there are found still no dominant reasons for determining the grade of malignancy and survival prognosis from the biological standpoint.
The condition of an estrogen receptor (ER) is one determining element for clinical and biological symptoms of human breast cancer. Adjuvant hormone therapeutics is usually effective in ER-positive breast cancer patients irrespective of age, condition in the menopause, correlation with axillary nodes, and tumor diameter. However, ER-negative breast cancer is resistance to this therapeutic method (J Clin Oncology (2001) 19, 3817-1827, Breast Cancer (2001) 8, 298-304). Patients having an ER-negative tumor necessarily show the same response to chemical therapy. Since existent indices cannot classify breast cancer of this type depending on clinical symptom, the postoperative prognosis is recognized to be various (J Natl Inst (1991) 83, 154-155, J Natl Cancer Inst (2000) 93, 979-989).
Prognosis of breast cancer patients with no lymph node metastasis (node-negative breast cancer; n0) is better than that of metastatic breast cancer patients. However, in Japan, the present inventors have found that 16% of node-negative breast cancer patients relapse within 5 years after the initial operation (Clin Cancer Res (2000) 6, 3193-3198).
Prediction of the postoperative prognosis of breast cancer patients shows increasing in importance from the standpoint of adjuvant therapeutics currently utilizable. A gene marker which is useful in identifying patients showing a possibility of relapsing after an operation gives a merit which suitable preoperative adjuvant therapeutics can be applied to a high risk patient, and enables prevention of occurrence of unnecessary, complicated and uncomfortable side effects.
Conventionally, postoperative procedures for individual patients are determined depending on tumor diameter and the stage, metastasis to a lymph node, diagnosis by clinicopathological factors, search of a hormone receptor, and the like, however, they are not critical methods (Cancer (1982) 50, 2131-2138, Histopathology (1991) 19, 403-410, Int J Cancer (1996) 69, 135-141, Am J Clin Oncol (1997) 20, 546-551, Eur J Cancer (2002) 38, 1329-1334, Jpn J Cancer Res (2000) 91, 293-300).
Recently, there is a prognosis marker for postoperative breast cancer patients, intending determination of an importance of mutations of genes. These gene mutations include a mutation of p53 (Breast Cancer Res Treat (2001) 69, 65-68), loss of heterozygosity in several alleles (Int J Clin Oncol (2001) 6, 6-12), and abnormal expressions of a BRCA2 gene (Int J Cancer (2002) 198, 879-882), WT1 gene (Clin Cancer Res (2002) 8, 1167-1171), HER2/neu gene (Arch Surg (2000) 135, 1469-1474) and Ki-67 gene (J Pathol (1999) 187, 207-216). However, these would not be recognized as effective prognosis predicting means when taking into consideration a fact which a cancer is a disease owing to accumulation of abnormalities of multiple genes.
Further, in these years, genome projects in various organisms are being progressed, and a lot of genes and their base sequences typically including a human gene are being clarified quickly. The function of a gene having a clarified sequence can be checked by various methods. As one of the effective methods, known is a gene expression analysis method utilizing clarified base sequence information. For example, there are developed methods utilizing various nucleic acid-nucleic acid hybridization reactions and various PCR reactions as typified by Northern Hybridization, and relations between various genes and expressions of their organism functions can be checked by these methods. Though the number of applicable genes is limited in these methods, there have been developed a methodology and a novel analysis method called DNA microarray method (DNA chip method) enabling lump expression analysis of multiple genes, for carrying out comprehensive and systemic analysis of extremely many genes such as one individual level, as being clarified recently through genome projects.
As the DNA microarray, a lot of shapes are known such as that in which DNA synthesis is conducted on many discrete cells applying a lithography technology (U.S. Pat. No. 5,445,934), that in which cells composed of grooves or holes are formed on a board and a probe is fixed to the inner wall of the cell (Tokkyo KOKAI (unexamined Japanese patent application) Nos. 11-108928, 2000-78998), a microarray in which a probe is fixed to a gel such as acrylamide and the like for increasing the amount of a probe to be fixed on a chip (U.S. Pat. No. 5,770,721, Tokkyo KOKAI No. 2000-60554), and the like.
Also known is a microarray obtained by fabricating a nucleic acid fixed gel retaining fiber array which retains a nucleic acid fixed gel, and cutting this array along a direction crossing the fiber axis of the array (Tokkyo KOKAI Nos. 2000-270878, 2000-270879).
Recent studies have found that a cDNA microarray technology is effective for identification of a novel gene marker for cancer diagnosis. To date, some researchers have carried out microarray analysis of breast cancer, however, there is no description about data of breast cancer gene expression property capable of predicting the postoperative prognosis of breast cancer (Proc Natl Acad Sci USA (1999) 96, 9212-9217, Nature (2000) 406, 747-752, Proc Natl Acad Sci USA (2001) 98, 11462-11467, Cancer Res (2001) 61, 5979-5984, Cancer Res (2000) 60, 2232-2238, Cancer Res (2001) 61, 5168-5178, Proc Natl Acad Sci USA (2001) 98, 10869-10874). As one exception, it is shown that a specific profile of a lymph node metastasis negative tumor gives a prediction of a short interval before progressing to distant metastasis (N Engl J Med (2002) 347, 1999-2009).